1. Field of the Invention
The present invention relates to a disk cartridge such as a magnetic disk cartridge, an optical disk cartridge, or a photomagnetic disk cartridge, and, more particularly, relates to a shutter mechanism for opening and closing head inserting apertures or read-write windows formed in a cartridge casing.
2. Description of the Related Art
For ease in handling, protection from dust and other purposes, a recording medium in the form of a disk, such as a magnetic disk or an optical disk, is loaded in a recording and reproducing apparatus for recording/reproducing information on/from the recording medium in a state in which the recording medium is accommodated in a cartridge casing. For this purpose, the cartridge casing is provided with head entry apertures or read-write windows to allow a head to access the disk recording medium when the cartridge casing is set in the recording and reproducing apparatus.
However, the head entry aperture thus provided may allow dust or the like to enter the cartridge casing and to adhere to a recording surface of the recording medium when the disk cartridge is not being used. In addition, when the disk cartridge is being handled, fingers or the like may possibly touch the recording surfaces of the disk cartridge through the head entry apertures. Consequently, dust, grease or the like could adhere to the recording surface, thereby making it impossible to effect favorable recording and reproduction. For this reason, the disk cartridge is usually provided with a shutter which closes the head entry holes when the disk is not being used.
FIG. 33 is a top plan view of an upper casing used in a conventional disk cartridge, while FIG. 34 is a front elevational view of the disk cartridge.
As shown in FIG. 34, a pair of slits 24 are formed separately on left- and right-hand sides of an end surface of a cartridge casing 1 comprising an upper casing member 2 and a lower casing member 3. These slits 24, 24 open to parts of a pair of triangular spring accommodating portions 23, 23 (see FIG. 33) formed inside the cartridge casing 1, and spring members are respectively inserted into and disposed in the spring accommodating portions 23, 23, as will be described later.
FIG. 35 is a diagram illustrating the relationship of engagement among the cartridge casing 1, a shutter 7, and spring members 25, 25.
As shown in the drawing, the shutter 7 is positioned at a substantially central portion of the cartridge casing 1 in such a manner that head entry apertures 6A, 6A in the cartridge casing 1 are closed by a closing cover portion 29. A pair of spring members 25, 25 are respectively disposed in the pair of spring accommodating portions 23, 23 (see FIG. 33) provided on both sides of the shutter 7. As shown in FIG. 36, the spring member 25 is a torsion coil spring having a coil portion 25A, a pair of arms 25B, 25B', and a pair of abutting portions 25C, 25C' respectively bent from the arms 25B, 25B'. In a state in which each of the spring member 25 is disposed in the cartridge case 1, as shown in FIG. 35, one of the abutting portions 25C, 25C' is engaged with a recess 14A (see FIG. 33) of the spring accommodating portion 23, while the other is engaged with a spring-engaging portion provided on a side surface of the shutter 7 or a stopper provided in the cartridge casing 1 (neither are shown).
This conventional disk cartridge is arranged such that the coil portion 25A of each spring member 25 is not fixed to the cartridge casing 1 and is movable inside the spring accommodating portion 23. For this reason, forces constantly act on the abutting portions 25C, 25C' of the spring member 25 in the sliding direction of the shutter 7. Consequently, the overall spring member 25 is constantly biased by a component of the force in the direction from the spring accommodating portion 23 toward the slit 24 (see FIG. 34), i.e., in the direction of springing out to the outside. Of the abutting portions 25C, 25C' of each of the spring members 25 disposed in the spring accommodating portions 23, the length of the one which is not engaged with a recess 14A (see FIG. 33) is made greater than the length of the slit 24, and the arrangement is such that said one abutting portion 25C or 25C' of the spring portion 25 bears against a front edge projection of the upper casing 2 and the lower casing 3 defining the slit 24.
However, if the slit 24 is expanded artificially or by some cause or other, forces restricting the spring member 25 disappear with the result that the spring member 25 disadvantageously springs out from the spring accommodating portion 23.